Compressor control system



March 29, 1938.

B. s. AIKMAN 2,112,414

COMPRESSOR CONTROL SYSTEM Filed Dec. l

INVENTOR E URTUN s. AIKMAN ATTORNEY March 29, 1938.

B. s. AIKMAN 2,112,414

COMPRESSOR CONTROL SYSTEM A Filed Dec. l, 1936 2 Sheets-Sheet 2 52 f [HM 1h56 l 56 52 Il@ G Ylml" HH 5 "Hu vf f 5' f-, 4 8l i J :y I 4o IST:

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59 2r 7g a eo 78 7o @l v 64 5 '4 w 7| l A l 75 65 l5 w 5 2 L *1 5a 26 I2 I 45 INVENTOR l BURTUN 5. AIKMAN d BY 52 49 f Ae 47 M 50 ATTORNEY Patented Mar. 2.9, 1938 'UNITED STATES PATENT OFFICE 2,112,414 COMPRESSOR CONTROL SYSTEM Application December 1, 1936, Serial No. 113,634

8 Claims.

This invention relates to control means for a fluid compressor, and is a continuation in part of my application, Serial No. 26,433, led June 13, 1935 for a Compressor governor.

It -is an object of this invention to provide means responsive to the pressure of the fluid compressed by a compressor for controlling the supply of current to an electric motor for driving the compessor, and for also controlling means to effectunloading of the compressor when it is started.

A further object of the invention is to provide means of the type described which is operable in response to relatively small pressure variations. Another object of the invention is to provide unloading means adapted for use on a fluid compressor not provided with unloading means.

A further object of the invention is to proide an improved compressor control system.

Other objects of the invention and features of novelty will be apparent from the following description taken in connection with'the accompanying drawings, in which Fig. 1 is a diagrammatic view showing a compressor equipped with control means embodying,

the device is conditioned to complete the circuit' to the driving motor for the compressor.

Fig; 3 is a view similar to Fig. 2 and showing the relationship of the parts. of the device when the device is'in the switchopen position, and

Fig. 4 is a fragmentary sectional view showing a modified form of valve device which I may employ.

Referring to Fig. 1 of the drawings, there is illustrated therein a compressor I, which is driven bymeans of an electric motor 2, and com.- presses fluid into a reservoir 4 through a pipe 6 having a check valve 'l interposed therein. The operation Of the compressor I is controlled by means of` a control device which is indicated generally by the reference numeral 8, and which controls the supply of current to the driving motor 2, and also controls the release of fluid under pressure from the pipe G for unloading the compressor in starting. A

'I'he compressor I Vmay be of any suitable well known construction and has an exhaust passage into which fluid is compressed, and to which the pipe 6 leading to the reservoir 4 is connected.

The control device 8 comprises a body or support I2 having a switch controlling lever I4 pivotally secured thereon by meansof a pin l5 which extends between ears I6 formed on the body I2. The lever I4 is yieldingly urged to move in a clockwise direction, as viewed in the drawings, into engagement with a portion I1 on the body I2 by means of a spring I8 which extends between a pin 20, which is secured to thebody i 2, and a V threaded link 2 I, which extends through the lever I4 and is adjustably secured thereto by means of a knurled nut 23. The lever I4 has a projecting portion 25 formed thereon and engageable with a stop 26 on the body I2 to limit movement of the lever in a counterclockwise direction.

The control device 8 includes a second lever 30 having one end thereof pivotally secured to the body I2 on a pin 3 I, and having a roller 32 pivotally 15 secured on the other end thereof and engageable with the free end of the lever I4. The lever 30 is urged to move in a counterclockwise direction by means of a spring 34 which has one end thereof secured to the body I2, and has its other end secured to a threaded link 36, which extends through the lever 38 and is adjustably secured relative thereto by means of a knurled nut 38.

When the switch controlling lever I4 is in the position in which it is shown in Fig. 2 of the drawings, the roller 32 on the lever 30 extends into a notch or recess 40 formed in the end of the lever I4, and when the lever I4 is in the position in which it is shown in Fig. 3 of the drawings, the roller 32 rests upon a cam surface 4I on the end of the lever I4.

The control `device 8 includes, in addition, a movable abutment in the form of a flexible diaphragm 45, which is clamped between the body I2 and a cover section`41. The diaphragm is sub- .35 ject on one side to the pressure of the fluid in a chamber 48 which communicates with the reservoir 4 by way of a pipe 49 and a restricted passage 50.

The diaphragm 45 has a follower 52 associated therewith andA engaging the exposed face thereof. This follower has a stem 53 formed integral therewith and terminating in a pointed end which exp tends into a recess 55 in the lever I4, the recess 55 being located adjacent to the pin I 5 on which the lever I4 is pivoted, but being spaced therefrom.

'I'he chamber 48 communicates by way Oi' the passage 58 with a. chamberI 59 formed in the body I2. Communication between the chamber 59 and the atmosphere by waylof a passage 60 is controlled by a valve 6I which is located in a bore in the body I2, and is urged into engagement with a seat surrounding the passage 60 by means of a spring 64.

The chambers 48 and 59 also communicate by way of the passage 58 and a pipe 68 with the pipe 6 at a point intermediate the compressor I and the check valve 1.

The switch controlling lever I4 has means associated therewith and controlling operation of the valve 6I. This means comprises a latch 18 positioned in an opening extending through the' lever I4 and pivotally secured to the lever I4 by' means of a pin 1 I. The latch 18 is urged to move in a counterclockwise direction against a stop 12 by means oi a coil spring 13located in a recess 14 in the lever I4.

.the end of the stem of the valve 6I.

The lever I4 has a vplunger 16 mounted in a bore therein, and the lower end of this plunger engages the latch 18, while the upper end thereof is engaged by the roller 32. The plunger 16 has an elongated opening 18 adjacent the mid-portion thereof through which the link 2| extends.

The body I2 has a pair o1' stationary contacts 88 associated therewith, one of these being shown in the drawings. These contacts are located on opposite sides of the switch controlling lever I4, and have arc shields 8I positioned on opposite sidesthereof. The stationary contacts 88 'are formed of suitable electrically conducting material, and are secured to, but insulated from, the body I2 and have connected thereto supply wires, one of which is indicated at 82, leading from a source of current supply.

The lever I4 also has a pair of movable contacts 85 associated therewith, one of these being shown in Fig. l of the drawings. One movable contact is located on each side of the lever I4. 'Ihe construction of the movable contact 85 is best shown in Fig. 1 of the drawings, where it will be seen that this contact isconstructed of a plurality of laminations of resilient, electrically conducting material, and terminates in a curved end portion adapted to engage a stationary contact 88. The movable contacts 85 are secured to, but insulated from, ears 81 which project from the lever I4, and are electrically connected by means of flexible conductors 88 with terminal blocks 98, which are adapted to have secured thereto wires 92 which are connected to the driving motor 2. 1

The movable contacts 85 are arranged so that when the lever I4 is in the position in which it is shown in Figs. 1 and 2 of the drawings, they will press ilrmly upon the stationary contacts 88 so as to establish good contact therewith.

In initially starting the compressor, the yfluid in the chamber 48 at the face of the diaphragm 45 is at a. relatively low pressure, and the switch lever I4 is held by the spring I8 in the position in which itis shown in Figs. 1 and 2 of the drawings. In this 'position of the lever I4, the movable contacts 85 are held in engagement with the stationary contacts 88 so as to complete-the circuit to the motor 2 for driving the compressor I. l

In this position of the lever I4, the roller 32 associated with the lever 38 is positioned in the notch or recess 48 in the upper end of the lever I4, while the latch 18 is out of engagement with 'I'he latch 18 is also held out of engagement with the stop 12 by the plunger 16, which is urged downwardly `by the roller 32, which engages the upper end of the plunger at this time.

As the circuit to the driving motor 2 is complete, the compressor will be operated and will compress fluid under pressure into `the pipe 6, through which it will ilow past the check valve 1 to the reservoir 4 to increase the pressure of the fluid in this reservoir. In addition, lluid under pressure supplied to the pipe 8 will flow by way of the pipe 65 and the passage 58 to the chamber 48 at the face of the diaphragm 48 so that the pressure of the fluid in the chamber 48 will be increased substantially as rapidly as the pressure of the iluid in the reservoir 4 is increased.

On an increase in the pressure of the iluid in the chamber 48, force is exerted through the diaphragm 45 and the follower 82 tending to move the lever I4 in a counterclockwise direction about the pin I5. This movement of the lever I4 is opposed by the spring I8, and by the spring 34, which resists the upward movement of the lever 38 which is required to lift the roller 32 out of the recess or notch 48 in which it is positioned.

When the pressure of the fluid in the chamber 48 and in the reservoir 4 has increased to a su!- ilcient value, the force exerted on the lever I4 and tending to move this lever in a counterclockwise direction is suihcient to overcome the forces opposing this movement, and the lever I4 will be moved, and in moving it Will cause the arm 38 to move in a clockwise direction so that the roller 32 is lifted out of the recess 48 in which it is positioned.

After a small amount of movement of the lever I4, the roller 32 will engage the cam surface 4I, which slopes away from the recess 48, and when the roller 32 is in engagement with this cam. surface it tends to assist movement of the lever I4 against the spring I8 away from the position in which it is shown in Fig. 2 of the drawings. This insures that the lever I4 will move very rapidly to the switch open position after it starts to move away from the switch closed position.

When the lever I4 moves, the movable contacts 85 are moved with it, and are moved out of engagement with the stationary contacts 88, thus interrupting the circuit to the driving motor 2 for the compressor I and interrupting operation of the compressor.

When the switch controlling lever I4 moves to the switch open position, which is the position in which it is shown in Fig. 3 of the drawings, the latch 18 is moved upwardly into engagement with the stop 12 by the spring 18 as the plunger 16 is no longer held by the roller 32.

On a reduction in the pressure of the iluid in the reservoir 4 as a result of the 'withdrawal of `the pipe 8 intermediate the check valve 1 and the compressor I, to a value below that of the fluid in the reservoir 4, as may occur due to leakage oi fluid past the exhaust valve of the compressor, iluid will ow-'to the chamber 48 and the connected portion of the pipe 8 from the reservoir 4 by way of the pipe 48 and the choke 58 to maintain the pressure of the iluid in the chamber 48 at substantially the same pressure as is present in the reservoir 4.

While the compressoris idle, therefore, the pressure of the fluid in the chamber 48 of the control device 8 will be maintained at substantially the same pressure as is present in the reservoir 4.

When the pressure of the fluid in the chamber 4 8 is reduced to a predetermined value, the force exerted thereby through the diaphragm 45 is insufficient to maintain the lever I4 against the opposing fo-rce of the spring I8. The spring- I8 will thereupon causethe lever I4 to move in a clockwise direction. After a small amount of movement of the lever I4 from the switch open position towards the switch closed position, the end of the latch 10 engages the end of the stem of the valve 6I, and on further movement of the lever I4 the latch 'I0 causes the valve 6I to move against the `spring 64, thereby permitting fluid to escapefroxn the chamber 59 to the atmosphere by way of the passage 60. The chamber 59 communicates with the chamber 48 by way of the passage 58, and also communicates by way of the pipe 65 with the portion of the pipe 6 intermedriate the check valve 'I and the compressor I. When the Valve 60 is open, therefore, fluid under pressure is released from the chamber 48 at the face of the diaphragm 45, and also from the portion of thepipe 6 adjacent the cornpressor I.

The passage 60 and the valve 6I are arranged so that the rate at which fluid is released from the chamber 59 and the connected volumes greatly exceeds the rate at which fluid is supplied to the chamber 48 from the reservoir 4 through the choke 50, so that when the valve 6I is unseated there will be a rapid reduction in the pressure of the fluid in the chamber 48 and in the portion of the pipe 6 adjacent the compressor i.

As a result of the reduction in the pressure of the fluid in the chamber 48 caused by the release of fluid therefrom, there will be a rapid reduction in the force exerted by the diaphragm 45 on the switch controlling lever I4, and the spring I8 will be able to move the switch controlling lever I4 towards the switch closed position very rapidly.

When the switch controlling lever it moves to the switch closed position, which is the position in which it is shown in Figs. l. and 2 of the drawings, the roller 32 is forced .into the recess 40 by the spring 34, and the roller engages the upper end of the plunger 16, forcing the plunger downwardly and moving the latch 'I0 against the spring 'I3 and out of engagement with the end of the valve Si. This permits the valve 6I to be moved to its seat by the spring B4 to cut olf the release of fluid under pressure from the chamber 59 and the connected volumes.

When the valve 6I is moved away from its seat so as to release fluid under pressure from the chamber 59, fluid is released from the pipe 65, and from the portion of the pipe 6 adjacent the compressor I,'so that when the switch controlling lever I4 moves to the closed position and current is supplied to the driving motor 2 of the compressor to. initiate operation of the compressor, there will be little opposition to operation of the compressor resulting from `the fluid pressure against which the compressor has to operate, as there will be little pressure in the pipe 6 into which the compressor discharges fluid. This reduces the load on the motor.2 in starting the compressor, and thereby eifects the unloading of the compressor during the starting period.

As a result of operation foi.' the compressor, fluid under pressure is supplied to the pipe 6, and flows therefrom by way of the pipe 65 and the passage 58 to the chamber 48 at the face of the diaphragm 45 and increases the pressure of the uid therein. The volume of this chamber and oi.' the pipe 65 is relativelyl small so that after a few revolutions of the compressor crankshaft the pressure of the fluid therein will be increased to a value exceeding that of the fluid in the reservoir 4, and iluid under pressure will thereupon flow through the check valve 1 from the compressor 'I to the reservoir 4. However, the pressure in the adiacent portion of the pipe 8 will not increase so as to greatly oppose operation of the compressor until the compressor has been operated for several revolutions, and this is suillcient to enable the driving motor to start ing motor, and to establish this supply, may be adjustably varied if desired. The control device also incorporates means b y which the difference between these pressures may be adjustably varied if desired.

The pressure which is effective to move the lever I 4 from the switch closed position to the switch open position may be adjustably varied by varying the tension on the spring I8, which is accomplished by adjusting the nut 23. k

The differential between the opening and closing pressures is governed by the spring 34 and may be adjustably varied by varying the adjustment of this spring, which is accomplished by y adjusting the nut 38.

ploy in place oi the valve i, which is employedv in the control device shown in Figs. 1 to 3 of the drawings. This valve device is mounted in a chamber 59a in the body I2a of the control device. This chamber is connected by way of a passage 58a with the chamber at the face of the diaphragm of the control device and with the pipe leading to the compressor.

The body lia of the control device has a bore therein in which is mounted a valve piston |00 having a sealing gasket secured on the face thereof, which is adapted to engage a seat rib l02 surrounding a passage Gila leading to the atmosphere. The face of the valve piston |00 outwardly of the seat rib l02is subject to the pressure of the fluid in the chamber 59a, while the valve piston F100 is subject on the other face to the pressure of the fluid in a chamber I04, which is constantly connected with the chamber 59a by means of a choke or restricted passage i06 extending through a wall in the body I2a of the control device.v A spring |08 extends between the Valve piston H00 and a threaded plug iI0 and yieldingly presses the valve piston |00 against the seat rib I02.

The Valve piston I00 has a passage extending therethrough, while a pilot valve 6Ia extends through this passage and carries a sealing gasket adapted to seat upon a seat rib III on the valve piston |00 surrounding the passage therethrough. A spring II2 extends between the pilot valve Gia and the threaded plug IIO, and yieldingly presses the pilot valve against the seat rib III on the valve piston |00.

The various parts oi" this valve device are arranged and proportioned so that the pilot valve 6 la occupies substantially the same position relative to the latch 10a as the valve 6I bears to the latch I0 in the device shown in Figs. 1 to 3 of the drawings.

Cil

In the operation of this valve device, when the switch lever Il is in the switch open position, the chambers 59m and |04 are charged with fluid under pressure at the pressure present in the reservoir as explained above. When the switch lever Il is moved towards the switch closed position, the latch 10a engages the end of the stem of the pilot valve Bla-and moves it against the spring 2, thereby opening communication from the chamber |04 through the passage in the valve piston |00 to the passage 60a and thence to the atmosphere. When the pilot valve Gla is moved away from its seat, the uid under pressure present in the chamber |04 may escape therefrom, thus reducing the force exerted thereby on the valve piston |00, and this valve piston will thereupon be moved against the spring |00 by the higher pressure of the fluid in the chamber 59a at the opposite face thereof.

On this movement of the valve piston |00, the sealing gasket carried thereby is moved away from the seat rib |02, thus opening a large communication between the chamber 59d and the atmosphere through the passage 60a to permit the rapid release of fluid under pressure from the chamber 59a, and also from the chamber at the face of the diaphragm of the control device and from the portion o! the discharge pipe adjacent the compressor. On the release o! fluid under pressure from the chamber 59a and the connected volumes there is a reduction in the force exerted on the switch lever Il, as explained above, and this lever is rapidly moved to the switch closed position, while the roller 32 extends into the notch 40 and presses upon the plunger 16 to move the latch 10a away from the end of thestem oi' the pilot valve lila. The pilot valve 6 la isthereupon moved into engagement with the seat rib I on the valve piston |00 by the spring |I2.

The valve piston |00, however, will not be moved against the seat rib |02 by the spring |00 assisted by the spring ||2, until the pressure of the fluid in the chamber 59a is reduced to a value insuillcient to maintain the valve piston |00 against the opposing i'orce of the springs |00 and I2, whereupon the valve piston 00 will be moved to the seated position to cut of! the further release of fluid under pressure from the chamber 59a and the connected volumes.

The various parts of the equipment are arranged and proportioned so that the valve piston |00 will not be moved into engagement with the seat rib |02 until the pressure of the fluid in the chamber 59a and the connected volumes has been reduced to a relatively small value. This insures that the pressure of the iluid in the portion of the pipe 6 ladjacent the compressor into which fluid ls compressed by the compressor will be at a relatively low value. and that there will be little opposition to operation of the compressor.

On the subsequent increase in the pressure of the fluid in the chamber 59a, fluid flows therefrom through the choke |00 to the chamber |04 at the spring side of the valve piston ma to 1ncrease the pressure of the uid in this chamber and assist the springs |00 and ||2 in maintaining the valve piston |00 in engagement with the seat rib |02 to prevent the release of iluid from the chamber 09a to the atmosphere through the passage 60a. At this time the pilot valve Cla. is held in the seated position by the spring ||2 so that iluid under pressure is not released from the chamber |04 to the passage 00a.

While one embodiment of the improved compressor control system provided by my invention, together with a modified form of valve device which I may employ in the control device employed in this system, have been illustrated and described in detail, it should be understood that the invention is not limited to these details of construction, and that numerous changes and modiilcations may be made without departing from the scope of the following claims.

Having now described my invention, what I claim as new and desire to secure by Letters Patent, is:

1. In combination, a uid compressor, a reservoir, a conduit connecting the discharge passage of the compressor with the reservoir, a check valve in said conduit and operable to permit fluid to flow from the compressor to the reservoir and to prevent the flow of iluid from the reservoir to the compressor, and a compressor governor comprising a switch adapted to control the circuit to the compressor driving motor, a member controlling operation of said switch, a body having a chamber therein, a movable abutment subject .to the pressure of the iluid in said chamber, the

abutment controlling said switch controlling member, means for supplying fluid under pressure to the chamber from the reservoir at a predetermined rate, means connecting the chamber with the conduit between the reservoirand the compressor at a point intermediate the compressor and the check valve, said means being adapted to permit iluid to ilow to said chamber at a more rapid rate than said predetermined rate, and means associated with the switch controlling member for releasing duid from said chamber at a rate more rapid than said predetermined rate.

2; In combination, a uid compressor, a. reservoir, a conduit connecting the discharge passage of the compressor with the reservoir, a check valve in said conduit and operable to permit iluid to flow from the compressor to the reservoir and to prevent the ilow of fluid from the reservoir to Athe compressor, and a compressor governor comprising a switch adapted to control a circuit to the compressor driving motor, a member controlling operation of said switch, a body having A a chamber therein, a movable abutment subject with the conduit between the compressor and the reservoir atA a point intermediate the compressor and the check valve and being adapted to permit uid to ilow to said chamber at a more rapid rate than said predetermined rate, and means operable on movement of the switch controlling member from the switch open position towards the switch closed position for releasing iluid from 'said chamber.

3. In combination,l a reservoir, a iluid compressor adapted to compress iluid into a communication through which iluid may be supplied to said reservoir, valve means operative to prevent back-flow oi' iluid from said reservoir to said communication, a valve device for releasing iluid from said communication, an electric motor for driving said compressor, a switch controlling the supply of current to said motor, and a movable abutment operated on an increase in the pressure oi' the fluid in said communication to eile'ct movement oi the switch to the open position to interrupt the supply of current to said motor. and operated on a reduction in the pressure of the fluid in said communication to elect movement of the switch to the closed position to supply current to said motor and to operate said valve device to release fluid from said communication.

4. In combination, a reservoir, a control chamber, a fluid compressor adapted to compress uid into said control chamber, a check valve operative to permit flow of fluid from said chamber to said reservoir and to prevent flow of fluid from the reservoir to said chamber, an electric motor for operating said compressor, a switch controlling the supply of current to said motor, valve means operative to vent iiuid from said control chamber, a movable abutment subject to and operated on an increase in the pressure of the fluid in said control chamber for opening said switch, said abutment being operated upon a predetermined reduction in said chamber pressure to eiTcct closing of the switch and to operate said valve means to release iiuid from said control chamber.

5. In combination, a reservoir, a control charnber, a fluid compressor adapted to compress iiuid into saidl` control chamber, a check valve operative to permit flow of fluid from said chamber to said reservoir and to prevent flow of iiuid from said reservoir to said chamber, an electric motor for operating said compressor, a switch controlling the supply of current to said motor, valve means operative to vent fluid from the control chamber at a predetermined rate, means for supplying uid under pressure from the reservoir to the control chamber at a rate less rapid than said predetermined rate, a movable abutment subject to and operated on an increase in the pressure of the uid in said control chamber for opening said switch, said abutment being operated on a predetermined reduction in said chamber pressure to effect closing of the switch and to operate the valve means to release fluid from said control chamber.

6. In combination, a reservoir, a control chamber, a fluid compressor adapted to compress uid into said control chamber, a, check valve operative to permit fluid to ow from the control chamber to the reservoir and to cut off the flow of iiuid from the reservoir to the control chamber, van electric motor for driving the compressor, a switch for controlling the supply of current to said motor, valve means for releasing fluid from said control chamber, a movable abutment subject to the pressure of the uid in said control chamber, a spring, a member subject to the opposing forces of said spring and of the force exerted by said abutment for operating said switch and said valve means, said member being operated upon an increase in fluid pressure in said`control chamber to open said switch, and being operated on a reduction in the pressure of the fluid in said control chamber to close the switch and to operate the valve means to release uid from the control chamber, and means to adjustably vary the force exerted by said spring on said member.

7. In combination, a reservoir, a control chamber, a fluid compressor adapted to compress fluid into said control chamber, a check valve operative to permit uid to flow from the control chamber to the reservoir and to cut off the flow of uid from the reservoir to the control chamber, an electric motor for driving the compressor, a switch for controlling the supply of current to said motor, valve means for releasing fluid from said control chamber at a predetermined rate, means for supplying fluid under pressure from the reservoir to the control chamber at a rate less rapid than said predetermined rate, a movable abutment subject to the pressure of the fluid in said control chamber, a spring, a member subject to the opposing forces of said spring and of the force exerted by said abutment for operating said switch and said valve means, said member being operated on an increase in fluid pressure in said control chamber to open said switch, and being operated on a reduction in the pressure of the fluid in said control chamber to close the switch and tooperate the valve means to release fluid from said control chamber, and means to adjustably vary the force exerted by said spring on said member.

8. In combination, a reservoir, a fluid compressor adapted to compress fluid into a communication through which fluid may be supplied to said reservoir, a check valve operative to prevent back' iiow of iiuid from said reservoir to said communication, an electric motor for driving said compressor, a switch for controlling the supply of current to said motor, an operating member for moving said switch between its open and closed positions, a movable abutment subject to and operated on an increase in the pressure of the fluid in said communication for moving said operating member from the switch closed position to the switch open position, said abutment being operated on a reduction in the pressure of the fluid in said communication to permit the switch operating member to be moved from the switch open position to the switch closed position, valve means operative by said switch operating member on movement thereof from the switch open position towards the switch closed position to release fluid under pressure from said communication, and' yielding resistance means associated with said operating member and operated on movement of said member to the switch open position to yieldingly resist movement of said member away from the switch open position towards the switch closed position.

BURTON S. AIKMAN. 

